This invention relates to a combinatorial weighing method and apparatus therefor. More particularly, the invention relates to a combinatorial weighing method and apparatus capable of holding, within allowable limits, the volume of weighed articles packaged in a weighing and packaging system having a combinatorial weighing apparatus and a packaging machine.
A weighing and packaging system includes a combinatorial weighing apparatus and a packaging machine. The combinatorial weighing apparatus computes combinations of weight values obtained from a plurality of weighing machines, selects a combination (referred to as the "optimum" combination") that gives a total combined weight value equal to a target weight value or closest to the target weight value within preset allowable limits, and discharges articles from those weighing machines corresponding to the selected combination. The packaging machine packages the articles discharged by the combinatorial weighing apparatus. Such a weighing and packaging system performs a highly accurate weighing operation and is very convenient in that the operations from weighing to the filling and packaging of bags or the like take place fully automatically.
Some articles, such as cornflakes, experience widely different degrees of swelling because of such processing conditions as applied temperature and material mixture. Such articles therefore differ in shape and size and vary greatly in apparent specific gravity. They also tend to crumble. When weighing out these articles combinatorially and then packaging them, there are instances where the volume of the packaged product is too large or too small, even though the weight of the articles in the bag or package is equal to the target weight value or closest to the target weight value within the preset limits. In other words, the change in volume of the packaged articles is in inverse proportion to the change in apparent specific gravity. Since the capacity of a package receiving the articles generally is fixed, too small a product volume in comparison with the package size gives the consumer the impression of a weight shortage. On the other hand, too large a product volume can lead to an improper seal because the package will be too full, and can cause the articles to overflow from the package and impair the packaging process. Accordingly, it is required that volume as well as weight be held within preset allowable limits. Until now, however, a control operation for holding the volume of a commodity within allowable limits has not been put into practice.